Hydrology and Water Resources in Arizona and the Southwest, Volume
12 (1982)

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Proceedings of the Hydrology section of the Annual Meeting of
the
Arizona-Nevada Academy of
Science. Full text manuscripts of work presented. Research
related to water resources, water management, and hydrologic
studies primarily focused regionally on southwestern US.

Volume 12. Proceedings of the 1982 Meetings of the Arizona
Section - American Water Resources Assn. and the Hydrology Section
- Arizona - Nevada Academy of Science.

A physiological model of nutrient uptake, based on membrane transport is combined with a phytoplankton biomass growth equation, based on internal nutrient limitation, to form a system of equations modeling phytoplankton growth which are capable of considerably richer dynamics than the Michaelis-Menton-Monod model (M³) or the Droop model. In particular, since the characteristic time scale of nutrient uptake is considerably faster than that of biomass increase, a singular perturbation problem results, leading to a relaxation oscillation similar to the van der Pol oscillator. In contrast with both the Michaelis-Mentor-Monod model and the Droop model, which were developed using steady state chemostat data, the present model would seem to be appropriate for batch cultures and lakes with long turnover times, where the assumptions of the chemostat steady state are not fulfilled. The qualitative behavior of the model compares favorably with data on batch growth of phytoplankton from the literature.

Gabbert, William A.; Ffolliott, Peter F.; Rasmussen, William O.; School of Renewable Natural Resources, The University of Arizona, Tucson, AZ 85721 (Arizona-Nevada Academy of Science, 1982-04-24)

A prototypical computer simulation model has been developed to aid watershed managers in estimating impacts of alternative land management practices on nutrient and heavy metal losses due to transported sediment on forested watersheds of the southwestern United States. The model, called SEDCON, allows users at remote locations with modest computer terminal equipment and commonly available data to obtain reliable estimates of nutrient and heavy metal concentrations in suspended sediment originating on uniformly-stocked, forested watersheds in the Southwest. SEDCON has been structured in an interactive mode to facilitate its use by persons not familiar with computer operations. Written in FORTRAN IV computer language, the model requires approximately 5000 words of core. SEDCON is operative on a DEC-10 computer at the University of Arizona.

The community of Tucson faces a tremendous future challenge regarding the management of its local water resources. With the advent of the new Groundwater Code and a plan to balance the basin by the year 2025, it is impossible to discuss the growth of the metropolitan area without first questioning the availability of adequate water resources. In Tucson, water will soon become the yardstick by which community expansion will be measured. The Tucson Water Utility plays a significant role in the management of the local water resource. Although there is currently complete reliance on groundwater, Tucson has received a tentative allocation of Colorado River water by means of the Central Arizona Project to supplement the groundwater supply in the future. In addition, the reuse of wastewater effluent and further conservation efforts must be planned in order to accommodate growth. The key ingredient to regional resource management, however, involves the cooperation that must exist among the major water-using entities of the area: Tucson Water, the mines, farmers, private water companies, and private well owners. This paper addresses the potential favorable and unfavorable impacts of limited water resources on future growth with respect to these concerns.

The 1980 Arizona Groundwater Management Act is the product of decades of court decisions and years of work and negotiation by representatives of the State's major water users, members of the State Legislature, and the Governor. The Act intends to conserve and manage the State's groundwater resources through the establishment of the Arizona Department of Water Resources (DWR). The Tucson Active Management Area (TAMA) is one of four geographical areas specifically designated within the legislation. There is established a Tucson office, locally staffed and administered by the DWR. The legislated goal for the TAMA is to balance groundwater withdrawal with dependable supplies by the year 2025. A series of time -specific management plans will incorporate conservation, supply augmentation, and farmland retirement to fulfill the 2025 goal. This paper discusses the existing and projected TAMA water supply/demand imbalance assuming no groundwater management and potential impacts of the Act on management and customers of the Tucson Water Utility. Specific positive impacts include increased public awareness, regional metered water use information, and reduction in groundwater overdraft. Specific negative impacts include more regulation, higher customer water rates, reduced water quality, and potential growth limitations.

The Gulf of California in northwestern Mexico is a tropical sea of the northeastern Pacific Ocean. Earthquake activity is common in the region, especially towards the northwest where transform faults are associated with volcanic and geothermal activity, and features such as the San Andreas fault zone. The Gulf contains 132,000 cu km of seawater, with a surface area of 162,000 sq km, and a mean depth of 815 m. Its surface salinity is about 35 ppt. The Gulf is subject to the second highest tides (>10 m in range) in North America. The region is currently undergoing extensive human development and energy exploration. After reviewing the climatic, geologic, soil and vegetation, and oceanographic settings, the potential energy resources of the Gulf are evaluated. These resources include those controlled by climate (solar, wind), geology (hydrocarbon, geothermal), biology (biomass) and oceanography (tidal, wave, hydrothermal). Climatic energy sources (unproven technology) have fair potential for modest-scale, onshore and near-use development. Geologic sources are online, and have high potential for large-scale commercial development with export value. Biological sources (unproven technology) have low potential for small-scale, near-use development. Oceanographic sources have high potential for moderate -scale near-use potentially exportable development.

Buras, Nathan; Department of Hydrology and Water Resources, University of Arizona, 85721 (Arizona-Nevada Academy of Science, 1982-04-24)

Water and energy interact strongly in Arizona. The Arizona State Water Plan mentions that under 1970 normalized conditions 60% of total use in the State was from groundwater aquifers, a proportion which may have increased in the last decade. The utilization of groundwater resources requires substantial amounts of power. In addition, the Central Arizona Project is an energy- intensive pr9ject: its Granite Reef aqueduct will require a pumping lift of 1,084 ft (352 m) using about 1.665 x 10⁹ kwh/year. The Tucson aqueduct component will have an additional lift of 997 ft (304 m). The hydropower installations planned within the CAP will have only limited generating capacities: Agua Fria 3 Mw, Granite Reef 3.5 Mw, and Maxwell 11 Mw. The remainder of the load will have to be picked up by thermal power plants and by pumped storage schemes which, by the year 2000, may need over 100,000 acre-feet per year to make up evaporative losses. Thus, energy is required to make water available to users, and water is a necessary ingredient in energy-related activities. These and other water-energy interactions in the Lower Colorado Basin are discussed.

Log-transmissivity, specific capacity, and water-level data from the Tajo River basin surrounding Madrid, Spain, are analyzed by geostatistical methods. The existing log-transmissivity data base is augmented with the aid of regression on log-specific capacities. The augmented set of data is used to obtain estimates of mean log- transmissivities over finite sub-regions of the aquifer by kriging. Kriging of water-level data at selected points in the aquifer is accomplished by removing the drift through an iterative generalized least squares procedure. The covariance matrices of the log-transmissivity and water-level estimation errors are used to investigate the structure of these errors.

Carrera, Jesus; Neuman, Shlomo P.; Department of Hydrology and Water Resources, University of Arizona, 85721 (Arizona-Nevada Academy of Science, 1982-04-24)

Groundwater flow in the Tajo River basin surrounding the city of Madrid is studied with the aid of a quasi three-dimensional model. The model is based on an efficient adaptive explicit-implicit finite element method recently described by Neuman et al. (1982). The top layer is unconfined and interacts with the Tajo River and its tributaries. Reproduction of the existing conditions in the aquifer demonstrates the existence of local and intermediate flow patterns which are superimposed on the regional flow pattern. Such flow patterns could not be identified with a conventional two-dimensional model. The manner in which these patterns are affected by topography and stream configuration is clearly illustrated with the aid of three-dimensional plots constructed from a certain viewing angle. Similar plots are used to illustrate the evolution of drawdown zones due to pumpage at predetermined locations in the aquifer.

A rotating boom rainfall simulator was used on 3 x 10.7 m plots to determine Universal Soil Loss Equation (USLE) parameter values. Simulator runs were made in the spring and fall of 1981 on two replications of four treatments on three soil types in southeastern Arizona. The treatments were: natural, vegetation removed, erosion pavement and vegetation removed, and tilled (moldboard plowed and disked). Runoff, infiltration, and soil loss varied significantly between treatments and, most interestingly, between the spring and fall runs. Plot surface characteristics of rock, gravel, soil, litter, and vegetation cover could not explain this seasonal variation in hydrologic response.

A method is presented for evaluating watershed conditions and alternative watershed treatments. A computer model simulates runoff responses from design storms. The model also simulates runoff changes due to management prescriptions that affect ground cover and structural treatments. Techniques are identified for setting watershed tolerance values for acceptable ground cover and establishing treatment priorities based on the inherent potentials of the watershed.

A 147-ha juniper watershed in north -central Arizona was sprayed with an herbicide mixture to kill all overstory vegetation. After the area was sprayed, annual water yield increased significantly when flow was greater than 12 mm. The ratio of mean annual quick flow to event flow prior to treatment was 0.86 and remained essentially the same after treatment. The herbicide treatment reduced evapotranspiration losses and increased water yield by killing the overstory trees and leaving them in place. These dead trees provided some shade and wind resistance and created a microclimate that reduced evaporation and enabled the soil below 30 cm to remain above its soil moisture wilting point. Although mean annual water yield increased by 27% (6 mm, 8-year mean), this increase may not be practical from a management view point. Therefore, it is unlikely that extensive juniper acreage will be treated. The amount of treated acreage will depend on the demand for water and on the value of water in the market place. The area treated will also be constrained by consideration of other resource values and desires of the public.

Gay, L. W.; Greenberg, Robert J.; School of Renewable Natural Resources, The University of Arizona, Tucson, AZ 85721 (Arizona-Nevada Academy of Science, 1982-04-24)

The Penman potential evapotranspiration model has been expanded and generalized for a vide range of climatic conditions by J. Doorenbos and W. 0. Pruitt (1975, FAO Irrig. & Drain. Pap. 24). Their comprehensive model relies heavily on tabulations and graphs to facilitate its application in remote areas where computer facilities are lacking. Future applications of this model have been substantially enhanced by our development of a program that runs on a HP-41C /CV calculator. The RPN program occupies 1778 bytes of memory, and will run on a 41CV, or a 41C with a quad memory module. A printer is also needed. The required climatic data can be input in a variety of forms, and program execution was planned with particular attention to the non- technical user. The entire calculator system (41CV, printer, card reader) cost less than $750, and provides for very portable use with a high degree of computing power.

Evapotranspiration (ET) from an extensive stand of saltcedar on the Colorado River floodplain was defined throughout the growing season by a series of Bowen ratio energy budget measurements in 1980 and 1981. The water table depth at the site near Blythe, California, was about 3 m during the two summers of measurement. Daily ET totals ranged from 2.9 mm/day in early April up to 11.0 mm/day in late June, and dropped down to 1.8 mm/day in late October. These values are means from two separate measurement systems, averaged over measurement periods of two to four days in length. The highest single day total measured by an individual system was 12.7 mm on June 28, 1981. The mid -summer ET rates from the saltcedar at this experimental site are substantial, and rank among the highest rates that have been reported elsewhere for irrigated cropland. The seasonal saltcedar water use of 1727 mm (including 90 mm of annual precipitation) is somewhat lower, however, than earlier, more speculative estimates for saltcedar that ranged up as high as 2100 mm per year.

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